1. Field of the Invention
The present invention relates to a covering device used for covering the open top of a vehicle container that is carried by or on trucks, trailers, roll-on/roll-off hoists, and similar vehicles.
2. Brief Description of the Related Art
It is well known in the industry to provide an automated means of covering the open top of a container that is carried on a vehicle such as a truck, trailer, roll-on/roll-off hoist, or similar vehicle. Such covers are particularly useful when transporting loose materials such as garbage, sand, or gravel, to prevent the load from being blown out of the container by the wind. Additionally, the cover protects the load from contamination. Many examples of container covers are known in the prior art. A popular arrangement for covering a truck container is to use a tarpaulin (or ‘tarp’) or other flexible cover, mounted upon a roller assembly adjacent one end of the truck container. The tarp is pulled from one end of the truck to the other by means of a front-to-rear pivot arm assembly.
There are many variations of pivot arm style covering assemblies that pull a flexible cover over the top of an open top container mounted to or carried on a truck chassis. Typically the pivot arms are powered between a first and second position on the truck by a spring force or hydraulic cylinders coupled directly to the pivot arms or in a rack-and-pinion arrangement in the vicinity of the pivot point. The pivot arms may be fixed in length or variable in length by way of a telescoping feature or other means. There is a cross-member or cover support element joining the outer ends of the pivot arms and attached to one end of the flexible cover. As the pivot arms move from the first position to the second position, the flexible cover is drawn over the opening of the container to cover it. As the pivot arms move from the second position to the first position, the flexible cover is retracted from the container, exposing the open top of the container. U.S. Pat. No. 5,829,818 introduces a device of this configuration having a hydraulic rack-and-pinion assembly at the pivot point to drive the pivot arms between first and second positions.
Another well known feature of automatic covering devices is telescopic pivot arms to cover varying length and height containers. One such device is disclosed in U.S. Pat. No. 4,874,196. This patent discloses a device that utilizes telescoping arms operated by hydraulic pistons inside the arms to extend and retract the length of the arms to ensure that the cover is pulled along the length of the container close to the upper edge of the container opening. U.S. Pat. No. 5,829,818 incorporates a rack-and-pinion device at the pivot point, together with telescopic arms having a piston rod and cylinder incorporated into each pivot arm for adjusting the covering device to accommodate varying size containers.
There are many disadvantages of dual telescoping pivot arms having hydraulic cylinders inside. First the pivot arms are very heavy from the weight of hydraulic hoses, fittings and cylinders inside the arms. This puts undue stress and fatigue on the components of the arms to counter the weight of the arms, especially when the arms are fully extended, thereby putting weight further out on the moment arm. Second, the pivot arms of automatic covering devices for trucks and trailers are very susceptible to damage. It is not unusual for the arms to be hit and bent during the loading process if the container is on the vehicle, or for the container to hit the arms when it is being loaded onto the chassis of a roll-on/roll-off container vehicle. When an arm is bent, the components inside the arms are normally bent or damaged in some way as well. This is very costly and can create a situation where the vehicle cannot be used until an arm repair is made.
Another problem with hydraulic lines and cylinders inside the arms is the fact that even when not damaged, hydraulic lines and components often leak hydraulic fluid which will fall to the ground creating an environmental problem and a nuisance to the public who may find hydraulic fluid on streets, driveways and sidewalks in their neighborhood.
These automatic vehicle covering devices most often have variable height towers in front of the container to support the front edge of the flexible cover. With hydraulic controls to operate the length of the pivot arms, the height of the variable height tower, and the pivot of the arms between the first and second positions, it becomes more complicated for the operator of the vehicle to operate the covering systems.
What is needed is a device for covering the opening of a vehicle container that is simple for the operator to use, can be repaired quickly when damaged and with less cost, and is environmentally friendly.